Modified conjugated diene-based polymer and method of preparing the same

ABSTRACT

The present invention relates to a modifier represented by Formula 1, a method of preparing the same, a modified conjugated diene-based polymer having a high modification ratio which includes a modifier-derived functional group, and a method of preparing the polymer.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a national phase entry under 35 U.S.C. § 371of International Application No. PCT/KR2017/012066 filed Oct. 30, 2017,which claims priority from Korean Patent Application Nos.10-2016-0144741, filed on Nov. 1, 2016, and 10-2017-0139991, filed onOct. 26, 2017, the disclosures of which are incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a modifier useful for polymermodification, a modified conjugated diene-based polymer including amodifier-derived functional group, and a method of preparing thepolymer.

BACKGROUND ART

In line with the recent demand for fuel-efficient cars, a conjugateddiene-based polymer having adjustment stability represented by wet skidresistance as well as low rolling resistance and excellent abrasionresistance and tensile properties is required as a rubber material for atire.

In order to reduce the rolling resistance of a tire, there is a methodof reducing a hysteresis loss of a vulcanized rubber, and reboundresilience at 50° C. to 80° C., tan δ, or Goodrich heat generation isused as an evaluation index of the vulcanized rubber. That is, it isdesirable to use a rubber material having high rebound resilience at theabove temperature or low tan δ or Goodrich heat generation.

A natural rubber, a polyisoprene rubber, or a polybutadiene rubber isknown as a rubber material having a low hysteresis loss, but theserubbers may have low wet skid resistance. Thus, recently, a conjugateddiene-based (co)polymer, such as a styrene-butadiene rubber(hereinafter, referred to as “SBR”) or a butadiene rubber (hereinafter,referred to as “BR”), is prepared by emulsion polymerization or solutionpolymerization to be used as a rubber for a tire.

In a case in which the BR or SBR is used as the rubber material for atire, the BR or SBR is typically used by being blended with a filler,such as silica or carbon black, to obtain physical properties requiredfor a tire. However, since an affinity of the Br or SBR with the filleris poor, physical properties, such as abrasion resistance, crackresistance, or processability, may rather be reduced.

Thus, as a method of increasing dispersibility of the SBR and the fillersuch as silica or carbon black, a method of modifying a polymerizationactive site of a conjugated diene-based polymer obtained by anionicpolymerization using organolithium with a functional group capable ofinteracting with the filler has been proposed. For example, a method ofmodifying a polymerization active end of a conjugated diene-basedpolymer with a tin-based compound or introducing an amino group, or amethod of modifying with an alkoxysilane derivative has been proposed.

Also, as a method of increasing dispersibility of the BR and the fillersuch as silica or carbon black, a method of modifying a living activeterminal with a specific coupling agent or modifier has been developedin a living polymer obtained by coordination polymerization using acatalyst composition which includes a lanthanide rare earth elementcompound.

However, since the BR or SBR modified by the above-described method hasa low terminal modification ratio, a physical property improvementeffect was insignificant with respect to a tire prepared by using thesame.

DISCLOSURE OF THE INVENTION Technical Problem

The present invention provides a modifier useful for polymermodification.

The present invention also provides a method of preparing the modifier.

The present invention also provides a modified conjugated diene-basedpolymer having a high modification ratio which includes amodifier-derived functional group.

The present invention also provides a method of preparing the modifiedconjugated diene-based polymer.

Technical Solution

According to an aspect of the present invention, there is provided amodifier represented by Formula 1.

In Formula 1,

R₁ is a monovalent hydrocarbon group having 1 to 20 carbon atoms; or amonovalent hydrocarbon group having 1 to 20 carbon atoms which includesat least one heteroatom selected from the group consisting of nitrogen(N), sulfur (S), and oxygen (O),

R₂ is a divalent hydrocarbon group having 1 to 20 carbon atoms which issubstituted or unsubstituted with at least one substituent selected fromthe group consisting of an alkyl group having 1 to 20 carbon atoms, acycloalkyl group having 3 to 20 carbon atoms, and an aryl group having 6to 30 carbon atoms; or a divalent hydrocarbon group having 1 to 20carbon atoms which includes at least one heteroatom selected from thegroup consisting of N, S, and O, and

R₃ and R₄ are each independently a monovalent hydrocarbon group having 1to 20 carbon atoms which is substituted or unsubstituted with at leastone substituent selected from the group consisting of an alkyl grouphaving 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbonatoms, and an aryl group having 6 to 30 carbon atoms, or R₃ and R₄ areconnected to each other to form an aliphatic or aromatic ring having 5to 20 carbon atoms.

According to another aspect of the present invention, there is provideda method of preparing a modifier represented by Formula 1 which includesthe steps of: performing a first reaction of a compound represented byFormula 2 and a halogen compound to prepare a salt-type compoundrepresented by Formula 3 (step a); performing a second reaction of thesalt-type compound represented by Formula 3 and an alkylamine to preparea compound represented by Formula 4 (step b); and performing a thirdreaction of the compound represented by Formula 4 and an alkyl ketonecompound (step c).

In Formulae 1 to 4,

R₁ is a monovalent hydrocarbon group having 1 to 20 carbon atoms; or amonovalent hydrocarbon group having 1 to 20 carbon atoms which includesat least one heteroatom selected from the group consisting of N, S, andO,

R₂ is a divalent hydrocarbon group having 1 to 20 carbon atoms which issubstituted or unsubstituted with at least one substituent selected fromthe group consisting of an alkyl group having 1 to 20 carbon atoms, acycloalkyl group having 3 to 20 carbon atoms, and an aryl group having 6to 30 carbon atoms; or a divalent hydrocarbon group having 1 to 20carbon atoms which includes at least one heteroatom selected from thegroup consisting of N, S, and O, and

R₃ and R₄ are each independently a monovalent hydrocarbon group having 1to 20 carbon atoms which is substituted or unsubstituted with at leastone substituent selected from the group consisting of an alkyl grouphaving 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbonatoms, and an aryl group having 6 to 30 carbon atoms, or R₃ and R₄ areconnected to each other to form an aliphatic or aromatic ring having 5to 20 carbon atoms.

According to another aspect of the present invention, there is provideda modified conjugated diene-based polymer including a functional groupderived from the modifier represented by Formula 1.

According to another aspect of the present invention, there is provideda method of preparing the modified conjugated diene-based polymer whichincludes the steps of: preparing an active polymer coupled with anorganometal by polymerization of a conjugated diene-based monomer in ahydrocarbon solvent in the presence of a catalyst composition includinga lanthanide rare earth element-containing compound (step 1); andreacting the active polymer with the modifier represented by Formula 1(step 2).

Advantageous Effects

Since a modifier represented by Formula 1 according to the presentinvention has high anionic reactivity due to the introduction of animine group, the modifier may easily react with an active site of apolymer, and thus, modification may be easily performed.

Also, a modified conjugated diene-based polymer according to the presentinvention may have excellent affinity with a filler, such as carbonblack, by including a function group derived from the modifierrepresented by Formula 1.

In addition, a method of preparing a modified conjugated diene-basedpolymer according to the present invention may easily prepare a modifiedconjugated diene-based polymer having a high modification ratio by usingthe modifier represented by Formula 1.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in more detail toallow for a clearer understanding of the present invention.

It will be understood that words or terms used in the specification andclaims shall not be interpreted as the meaning defined in commonly useddictionaries. It will be further understood that the words or termsshould be interpreted as having a meaning that is consistent with theirmeaning in the context of the relevant art and the technical idea of theinvention, based on the principle that an inventor may properly definethe meaning of the words or terms to best explain the invention.

The present invention provides a modifier useful for modification of amodified conjugated diene-based polymer.

The modifier according to an embodiment of the present invention isrepresented by Formula 1 below.

In Formula 1,

R₁ is a monovalent hydrocarbon group having 1 to 20 carbon atoms; or amonovalent hydrocarbon group having 1 to 20 carbon atoms which includesat least one heteroatom selected from the group consisting of nitrogen(N), sulfur (S), and oxygen (O),

R₂ is a divalent hydrocarbon group having 1 to 20 carbon atoms which issubstituted or unsubstituted with at least one substituent selected fromthe group consisting of an alkyl group having 1 to 20 carbon atoms, acycloalkyl group having 3 to 20 carbon atoms, and an aryl group having 6to 30 carbon atoms; or a divalent hydrocarbon group having 1 to 20carbon atoms which includes at least one heteroatom selected from thegroup consisting of N, S, and O, and

R₃ and R₄ are each independently a monovalent hydrocarbon group having 1to 20 carbon atoms which is substituted or unsubstituted with at leastone substituent selected from the group consisting of an alkyl grouphaving 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbonatoms, and an aryl group having 6 to 30 carbon atoms, or R₃ and R₄ areconnected to each other to form an aliphatic or aromatic ring having 5to 20 carbon atoms.

Specifically, R₁ in Formula 1 may be a monovalent hydrocarbon grouphaving 1 to 20 carbon atoms, or a monovalent hydrocarbon group having 1to 20 carbon atoms which includes at least one heteroatom selected fromthe group consisting of N, S, and O.

In a case in which R₁ is a monovalent hydrocarbon group having 1 to 20carbon atoms, R₁ may be one selected from the group consisting of analkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to20 carbon atoms, an aryl group having 6 to 20 carbon atoms, and anarylalkyl group having 7 to 20 carbon atoms, and R₁ may specifically beone selected from the group consisting of an alkyl group having 1 to 10carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, an arylgroup having 6 to 12 carbon atoms, and an arylalkyl group having 7 to 12carbon atoms.

Also, in a case in which R₁ is a monovalent hydrocarbon group having 1to 20 carbon atoms which includes a heteroatom, R₁ may be one includinga heteroatom instead of at least one carbon atom in the hydrocarbongroup; or may be one in which at least one hydrogen atom bonded to acarbon atom in the hydrocarbon group is substituted with a heteroatom ora functional group including a heteroatom, wherein the heteroatom may beone selected from the group consisting of N, O, and S. Specifically, ina case in which R₁ is a monovalent hydrocarbon group having 1 to 20carbon atoms which includes a heteroatom, R₁ may be an alkoxy group; aphenoxy group; a carboxy group; an acid anhydride group; an amino group;an amide group; an epoxy group; a mercapto group; —[R¹¹O]_(x)R¹² (whereR¹¹ is an alkylene group having 2 to 20 carbon atoms, R¹² is selectedfrom the group consisting of a hydrogen atom, an alkyl group having 1 to20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an arylgroup having 6 to 20 carbon atoms, and an arylalkyl group having 7 to 20carbon atoms, and x is an integer of 2 to 10); and a monovalenthydrocarbon group (e.g., hydroxyalkyl group, alkoxyalkyl group,phenoxyalkyl group, aminoalkyl group, or a thiolalkyl group) having 1 to20 carbon atoms which includes at least one functional group selectedfrom the group consisting of a hydroxy group, an alkoxy group, a phenoxygroup, a carboxy group, an ester group, an acid anhydride group, anamino group, an amide group, an epoxy group, and a mercapto group. Forexample, in a case in which R₁ is an alkyl group having 1 to 20 carbonatoms which includes a heteroatom, R₁ may be one selected from the groupconsisting of an alkoxy group having 1 to 20 carbon atoms, analkoxyalkyl group having 2 to 20 carbon atoms, a phenoxyalkyl grouphaving 7 to 20 carbon atoms, an aminoalkyl group having 1 to 20 carbonatoms, and —[R¹¹O]_(x)R¹² (where R¹¹ is an alkylene group having 2 to 20carbon atoms, R¹² is selected from the group consisting of a hydrogenatom, an alkyl group having 1 to 10 carbon atoms, a cycloalkyl grouphaving 3 to 12 carbon atoms, an aryl group having 6 to 18 carbon atoms,and an arylalkyl group having 7 to 18 carbon atoms, and x is an integerof 2 to 10).

Furthermore, in Formula 1, R₂ may be a divalent hydrocarbon group having1 to 20 carbon atoms or a divalent hydrocarbon group having 1 to 20carbon atoms which includes at least one heteroatom selected from thegroup consisting of N, S, and O.

In a case in which R₂ is a divalent hydrocarbon group having 1 to 20carbon atoms, R₂ may be an alkylene group having 1 to 10 carbon atomssuch as a methylene group, an ethylene group, or a propylene group; anarylene group having 6 to 20 carbon atoms such as a phenylene group; oran arylalkylene group having 7 to 20 carbon atoms as a combination groupthereof. Specifically, R₂ may be an alkylene group having 1 to 6 carbonatoms. Also, R₂ may be one substituted with at least one substituentselected from the group consisting of an alkyl group having 1 to 20carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, and anaryl group having 6 to 30 carbon atoms.

Furthermore, in a case in which R₂ is a divalent hydrocarbon grouphaving 1 to 20 carbon atoms which includes a heteroatom, R₂ may be oneincluding a heteroatom instead of at least one carbon atom in thehydrocarbon group; or may be one in which at least one hydrogen atombonded to a carbon atom in the hydrocarbon group is substituted with aheteroatom or a functional group including a heteroatom, wherein theheteroatom may be one selected from the group consisting of N, O, and S.

Specifically, in a case in which R₂ is a divalent hydrocarbon grouphaving 1 to 20 carbon atoms which includes a heteroatom, R₂ may be adivalent hydrocarbon group having 1 to 20 carbon atoms which includes atleast one functional group selected from the group consisting of analkoxy group; a phenoxy group; a carboxy group; an acid anhydride group;an amino group; an amide group; an epoxy group; a mercapto group; ahydroxy group, an ester group.

Also, in Formula 1, R₃ and R₄ may each independently be a monovalenthydrocarbon group having 1 to 20 carbon atoms, or may be connected toeach other to form an aliphatic or aromatic ring having 5 to 20 carbonatoms, and, specifically, R₃ and R₄ may each independently be an alkylgroup having 1 to 10 carbon atoms which is substituted or unsubstitutedwith an alkyl group having 1 to 10 carbon atoms. For example, R₃ and R₄may each independently be an alkyl group having 1 to 6 carbon atomswhich is substituted or unsubstituted with an alkyl group having 1 to 5carbon atoms.

Specifically, in the modifier of Formula 1, R₁ may be one selected fromthe group consisting of an alkyl group having 1 to 10 carbon atoms, acycloalkyl group having 3 to 12 carbon atoms, an aryl group having 6 to12 carbon atoms, an arylalkyl group having 7 to 12 carbon atoms, analkoxyalkyl group having 2 to 10 carbon atoms, a phenoxyalkyl grouphaving 7 to 12 carbon atoms, and an aminoalkyl group having 1 to 10carbon atoms, R₂ may be an alkylene group having 1 to 10 carbon atoms,and R₃ and R₄ may each independently be an alkyl group having 1 to 10carbon atoms which is substituted or unsubstituted with an alkyl grouphaving 1 to 10 carbon atoms. For example, in Formula 1, R₁ may be oneselected from the group consisting of an alkyl group having 1 to 10carbon atoms, an alkoxyalkyl group having 2 to 10 carbon atoms, and aphenoxyalkyl group having 7 to 12 carbon atoms, R₂ may be an alkylenegroup having 1 to 6 carbon atoms, and R₃ and R₄ may each independentlybe an alkyl group having 1 to 6 carbon atoms which is substituted orunsubstituted with an alkyl group having 1 to 5 carbon atoms.

Specifically, the modifier represented by Formula 1 may include thoserepresented by the following Formulae 1-1 to 1-4.

Also, the modifier may have a solubility in 100 g of a non-polarsolvent, for example, hexane, of 10 g or more at 25° C. and 1atmosphere. Herein, the solubility of the modifier denotes a degree towhich the modifier is clearly dissolved without a turbidity phenomenonduring visual observation. Since the modifier has high solubility asdescribed above, a high modification ratio for the polymer may beachieved.

The modifier represented by Formula 1 according to the present inventionmay easily modify a conjugated diene-based polymer at a highmodification ratio by including a reactive functional group for theconjugated diene-based polymer, a filler affinity functional group, anda solvent affinity functional group, and may improve abrasionresistance, low fuel consumption property, and processability of arubber composition including the polymer and a molded article, such as atire, prepared therefrom. Specifically, the modifier of Formula 1 mayinclude an imine group and an aliphatic hydrocarbon group in themolecule as described above, and, since the imine group may modify theconjugated diene-based polymer at a high modification ratio by having ahigh reactivity with an active site of the conjugated diene-basedpolymer, the functional group substituted with the modifier may beintroduced into the conjugated diene-based polymer in a high yield.Also, the imine group may further improve affinity with a filler,particularly, carbon black, while reacting with a conjugated diene-basedpolymer end to be converted to a secondary amino group. Furthermore, thealiphatic hydrocarbon group, particularly, a linear aliphatichydrocarbon group may increase solubility of the modifier by improvingaffinity with a polymerization solvent, and thus, may improve amodification ratio with respect to the conjugated diene-based polymer.In addition, in the modifier, the hydrocarbon group including aheteroatom, specifically, a tertiary amino group may improve affinity ofthe modified conjugated diene-based polymer with the filler in therubber composition. For example, since the tertiary amino group mayprevent agglomeration of the filler by disturbing a hydrogen bondbetween hydroxide groups present on the surface of the filler, thetertiary amino group may improve dispersibility of the filler in therubber composition.

Furthermore, the present invention provides a method of preparing themodifier represented by Formula 1.

The method of preparing the modifier according to an embodiment of thepresent invention includes the steps of: performing a first reaction ofa compound represented by Formula 2 and a halogen compound to prepare asalt-type compound represented by Formula 3 (step a); performing asecond reaction of the salt-type compound represented by Formula 3 andan alkylamine to prepare a compound represented by Formula 4 (step b);and performing a third reaction of the compound represented by Formula 4and an alkyl ketone compound (step c).

In Formulae 1 to 4,

R₁ is a monovalent hydrocarbon group having 1 to 20 carbon atoms; or amonovalent hydrocarbon group having 1 to 20 carbon atoms which includesat least one heteroatom selected from the group consisting of N, S, andO,

R₂ is a divalent hydrocarbon group having 1 to 20 carbon atoms which issubstituted or unsubstituted with at least one substituent selected fromthe group consisting of an alkyl group having 1 to 20 carbon atoms, acycloalkyl group having 3 to 20 carbon atoms, and an aryl group having 6to 30 carbon atoms; or a divalent hydrocarbon group having 1 to 20carbon atoms which includes at least one heteroatom selected from thegroup consisting of N, S, and O, and

R₃ and R₄ are each independently a monovalent hydrocarbon group having 1to 20 carbon atoms which is substituted or unsubstituted with at leastone substituent selected from the group consisting of an alkyl grouphaving 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbonatoms, and an aryl group having 6 to 30 carbon atoms, or R₃ and R₄ areconnected to each other to form an aliphatic or aromatic ring having 5to 20 carbon atoms.

The first reaction of step a is a step for preparing a salt-typecompound represented by Formula 3, wherein the first reaction may beperformed by reacting a compound represented by Formula 2 with a halogencompound.

Also, the second reaction of step b is a step for preparing a compoundrepresented by Formula 4, wherein the second reaction may be performedby reacting the salt-type compound represented by Formula 3 with analkylamine. In this case, the first reaction of step a and the secondreaction of step b may be continuously performed in one reactor or maybe stepwise performed in two reactors.

The first reaction and the second reaction may be respectively performedin the presence of a polar solvent at low temperature. In this case, inthe first reaction, the compound represented by Formula 2 and thehalogen compound may be used in a stoichiometric ratio, and,specifically, the compound represented by Formula 2 and the halogencompound may be used at a molar ratio of 1:0.9 to 1:1. Also, in thesecond reaction, the salt-type compound represented by Formula 3 and thealkylamine may be used in a stoichiometric ratio, and, specifically, thesalt-type compound represented by Formula 3 and the alkylamine may beused at a molar ratio of 1:1.5 to 1:3.

Herein, the low temperature in the first reaction and the secondreaction may each independently be in a temperature range of −10° C. to25° C., and the first reaction and the second reaction may be performedat the same temperature or may be performed at different temperatures.

Furthermore, the polar solvent used in the first reaction and the secondreaction may each independently be at least one selected from methanol,ethanol, butanol, hexanol, and dichloromethane.

Specifically, the polar solvent used in the first reaction may haverelatively stronger polarity than the polar solvent used in the secondreaction, wherein the polar solvent used in the first reaction mayparticularly be at least one selected from methanol, ethanol, butanol,and hexanol, and may more particularly be ethanol, and the polar solventused in the second reaction may be dichloromethane.

Also, the halogen compound is not particularly limited, but, forexample, may be thionyl chloride.

Furthermore, the alkylamine is not particularly limited, but, forexample, may be triethylamine.

The third reaction of step c is a step for preparing the modifierrepresented by Formula 1, wherein the third reaction may be performed byreacting a compound represented by Formula 4 with an alkyl ketonecompound. In this case, the third reaction may be performed at hightemperature, and the compound represented by Formula 4 and the alkylketone compound may be used in a stoichiometric ratio.

Specifically, the third reaction may be performed in a temperature rangeof 100° C. to 150° C., and the compound represented by Formula 4 and thealkyl ketone compound may be used at a molar ratio of 1:1 to 1:5.

Also, the alkyl ketone compound is not particularly limited, but, forexample, may be at least one selected from the group consisting ofmethyl isopropyl ketone, methyl isobutyl ketone, cyclohexanone, methylethyl ketone, diisopropyl ketone, ethyl butyl ketone, methyl butylketone, and dipropyl ketone.

In addition, the present invention provides a modified conjugateddiene-based polymer including a functional group derived from a modifierrepresented by Formula 1 below.

In Formula 1,

R₁ is a monovalent hydrocarbon group having 1 to 20 carbon atoms; or amonovalent hydrocarbon group having 1 to 20 carbon atoms which includesat least one heteroatom selected from the group consisting of N, S, andO,

R₂ is a divalent hydrocarbon group having 1 to 20 carbon atoms which issubstituted or unsubstituted with at least one substituent selected fromthe group consisting of an alkyl group having 1 to 20 carbon atoms, acycloalkyl group having 3 to 20 carbon atoms, and an aryl group having 6to 30 carbon atoms; or a divalent hydrocarbon group having 1 to 20carbon atoms which includes at least one heteroatom selected from thegroup consisting of N, S, and O, and

R₃ and R₄ are each independently a monovalent hydrocarbon group having 1to 20 carbon atoms which is substituted or unsubstituted with at leastone substituent selected from the group consisting of an alkyl grouphaving 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbonatoms, and an aryl group having 6 to 30 carbon atoms, or R₃ and R₄ areconnected to each other to form an aliphatic or aromatic ring having 5to 20 carbon atoms.

The modified conjugated diene-based polymer according to an embodimentof the present invention may be prepared by reacting an active polymercoupled with an organometal with the modifier represented by Formula 1through a preparation method to be described later, and physicalproperties of the modified conjugated diene-based polymer may beimproved by including the functional group derived from the modifierrepresented by Formula 1.

Specifically, the modifier represented by Formula 1 may be the same asdescribed above.

Specifically, the modified conjugated diene-based polymer may include afiller affinity functional group and a solvent affinity functional groupby including the functional group derived from the modifier representedby Formula 1, and thus, abrasion resistance, low fuel consumptionproperty, and processability of a rubber composition including themodified conjugated diene-based polymer and a molded article, such as atire, prepared therefrom may be improved.

The modified conjugated diene-based polymer may have a number-averagemolecular weight (Mn) of 100,000 g/mol to 700,000 g/mol, for example,120,000 g/mol to 500,000 g/mol.

Also, the modified conjugated diene-based polymer may have aweight-average molecular weight (Mw) of 300,000 g/mol to 1,200,000g/mol, for example, 400,000 g/mol to 1,000,000 g/mol.

Furthermore, the modified conjugated diene-based polymer may have amolecular weight distribution (Mw/Mn) of 1.05 to 5.

In addition, in consideration of an improvement in balance betweenmechanical properties, an elastic modulus, and processability of therubber composition when the modified conjugated diene-based polymeraccording to the embodiment of the present invention is used in therubber composition, the weight-average molecular weight and thenumber-average molecular weight may satisfy the above-described rangesat the same time while the modified conjugated diene-based polymer hasthe above-described molecular weight distribution range.

Specifically, the modified conjugated diene-based polymer may have amolecular weight distribution of 3.4 or less, a weight-average molecularweight of 300,000 g/mol to 1,200,000 g/mol, and a number-averagemolecular weight of 100,000 g/mol to 700,000 g/mol, and, for example,may have a polydispersity of 3.2 or less, a weight-average molecularweight of 400,000 g/mol to 1,000,000 g/mol, and a number-averagemolecular weight of 120,000 g/mol to 500,000 g/mol.

Herein, each of the weight-average molecular weight and thenumber-average molecular weight is a polystyrene-equivalent molecularweight analyzed by gel permeation chromatography (GPC), and themolecular weight distribution (Mw/Mn) is also known as polydispersity,wherein it was calculated as a ratio (Mw/Mn) of the weight-averagemolecular weight (Mw) to the number-average molecular weight (Mn).

Also, the modified conjugated diene-based polymer according to theembodiment of the present invention may be a polymer having highlinearity in which a value of −S/R (stress/relaxation) at 100° C. is 0.7or more. In this case, the −S/R denotes a change in stress in responseto the same amount of strain generated in a material, wherein it is anindex indicating linearity of a polymer. Normally, the linearity of thepolymer is low as the −S/R value is reduced, and rolling resistance orrotation resistance when the polymer is used in the rubber compositionis increased as the linearity is reduced. Furthermore, branching degreeand molecular weight distribution of the polymer may be estimated fromthe −S/R value, and the higher the −S/R value is, the higher thebranching degree is and the wider the molecular weight distribution is.As a result, processability of the polymer is excellent, but mechanicalproperties are low.

Since the modified conjugated diene-based polymer according to theembodiment of the present invention has a high −S/R value of 0.7 or moreat 100° C. as described above, resistance characteristics and fuelconsumption property may be excellent when used in the rubbercomposition. Specifically, the −S/R value of the modified conjugateddiene-based polymer may be in a range of 0.7 to 1.0.

Herein, the −S/R value was measured with a large rotor at a rotor speedof 2±0.02 rpm at 100° C. using a Mooney viscometer, for example, MV2000Eby Monsanto Company. Specifically, after the polymer was left standingfor 30 minutes or more at room temperature (23±3° C.), 27±3 g of thepolymer was taken and filled into a die cavity, and Mooney viscosity wasmeasured while applying a torque by operating a platen. Then, the −S/Rvalue was obtained by measuring a slope of change in the Mooneyviscosity obtained while the torque was released for additional 1minute.

Also, specifically, the modified conjugated diene-based polymer may havea cis-1,4 bond content of a conjugated diene portion, which is measuredby Fourier transform infrared spectroscopy (FT-IR), of 95% or more, forexample, 98% or more. Thus, abrasion resistance, crack resistance, andozone resistance of the rubber composition may be improved when used inthe rubber composition.

Furthermore, the modified conjugated diene-based polymer may have avinyl content of the conjugated diene portion, which is measured byFourier transform infrared spectroscopy, of 5% or less, for example, 2%or less. In a case in which the vinyl content in the polymer is greaterthan 5%, the abrasion resistance, crack resistance, and ozone resistanceof the rubber composition including the same may be deteriorated.

Herein, the cis-1,4 bond content and vinyl content in the polymer aremeasured by the Fourier transform infrared spectroscopy (FT-IR) inwhich, after measuring a FT-IR transmittance spectrum of a carbondisulfide solution of the conjugated diene-based polymer which isprepared at a concentration of 5 mg/mL by using disulfide carbon of thesame cell as a blank, each content was obtained by using a maximum peakvalue (a, base line) near 1,130 cm⁻¹ of the measurement spectrum, aminimum value (b) near 967 cm⁻¹ which indicates a trans-1,4 bond, aminimum value (c) near 911 cm⁻¹ which indicates a vinyl bond, and aminimum value (d) near 736 cm⁻¹ which indicates a cis-1,4 bond.

In addition, the present invention provides a method of preparing amodified conjugated diene-based polymer including a functional groupderived from the modifier represented by Formula 1.

The preparation method according to an embodiment of the presentinvention includes the steps of: preparing an active polymer coupledwith an organometal by polymerization of a conjugated diene-basedmonomer in a hydrocarbon solvent in the presence of a catalystcomposition including a lanthanide rare earth element-containingcompound (step 1); and reacting the active polymer with a modifierrepresented by Formula 1 (step 2)

In Formula 1, R₁ is a monovalent hydrocarbon group having 1 to 20 carbonatoms; or a monovalent hydrocarbon group having 1 to 20 carbon atomswhich includes at least one heteroatom selected from the groupconsisting of N, S, and O, R₂ is a divalent hydrocarbon group having 1to 20 carbon atoms which is substituted or unsubstituted with at leastone substituent selected from the group consisting of an alkyl grouphaving 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbonatoms, and an aryl group having 6 to 30 carbon atoms; or a divalenthydrocarbon group having 1 to 20 carbon atoms which includes at leastone heteroatom selected from the group consisting of N, S, and O, and R₃and R₄ are each independently a monovalent hydrocarbon group having 1 to20 carbon atoms which is substituted or unsubstituted with at least onesubstituent selected from the group consisting of an alkyl group having1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms,and an aryl group having 6 to 30 carbon atoms, or R₃ and R₄ areconnected to each other to form an aliphatic or aromatic ring having 5to 20 carbon atoms.

Specifically, the modifier represented by Formula 1 may be the same asdescribed above.

Step 1 is a step for preparing an active polymer coupled with anorganometal by using a catalyst composition including a lanthanide rareearth element-containing compound, wherein step 1 may be performed bypolymerization of a conjugated diene-based monomer in a hydrocarbonsolvent in the presence of the catalyst composition.

The conjugated diene-based monomer is not particularly limited, but, forexample, may be at least one selected from the group consisting of1,3-butadiene, 2,3-dimethyl-1,3-butadiene, piperylene,3-butyl-1,3-octadiene, isoprene, and 2-phenyl-1,3-butadiene.

The hydrocarbon solvent is not particularly limited, but, for example,may be at least one selected from the group consisting of n-pentane,n-hexane, n-heptane, isooctane, cyclohexane, toluene, benzene, andxylene.

The catalyst composition may be used in an amount such that thelanthanide rare earth element-containing compound is included in anamount of 0.1 mmol to 0.5 mmol based on total 100 g of the conjugateddiene-based monomer, and may specifically be used in an amount such thatthe lanthanide rare earth element-containing compound is included in anamount of 0.1 mmol to 0.4 mmol, for example, 0.1 mmol to 0.25 mmol,based on total 100 g of the conjugated diene-based monomer. Since thepreparation method according to the embodiment of the present inventionuses the catalyst composition within the above range, catalytic activityis high and an appropriate catalyst concentration is provided, and thus,it is not necessary to carry out a separate demineralization process.

The lanthanide rare earth element-containing compound is notparticularly limited, but, for example, may be at least one compound ofrare earth metals with an atomic number of 57 to 71, such as lanthanum,neodymium, cerium, gadolinium, or praseodymium, and may specifically bea compound including at least one selected from the group consisting ofneodymium, lanthanum, and gadolinium.

Also, the lanthanide rare earth element-containing compound may includecarboxylates containing the above-described rare earth element (e.g.,neodymium acetate, neodymium acrylate, neodymium methacrylate, neodymiumgluconate, neodymium citrate, neodymium fumarate, neodymium lactate,neodymium maleate, neodymium oxalate, neodymium 2-ethylhexanoate, orneodymium neodecanoate); organophosphates containing the above-describedrare earth element (e.g., neodymium dibutyl phosphate, neodymiumdipentyl phosphate, neodymium dihexyl phosphate, neodymium diheptylphosphate, neodymium dioctyl phosphate, neodymium bis(1-methylheptyl)phosphate, neodymium bis(2-ethylhexyl) phosphate, or neodymium didecylphosphate); organophosphonates containing the above-described rare earthelement (e.g., neodymium butyl phosphonate, neodymium pentylphosphonate, neodymium hexyl phosphonate, neodymium heptyl phosphonate,neodymium octyl phosphonate, neodymium (1-methylheptyl) phosphonate,neodymium (2-ethylhexyl) phosphonate, neodymium decyl phosphonate,neodymium dodecyl phosphonate, or neodymium octadecyl phosphonate);organophosphinates containing the above-described rare earth element(e.g., neodymium butylphosphinate, neodymium pentylphosphinate,neodymium hexylphosphinate, neodymium heptylphosphinate, neodymiumoctylphosphinate, neodymium (1-methylheptyl)phosphinate, or neodymium(2-ethylhexyl)phosphinate); carbamates containing the above-describedrare earth element (e.g., neodymium dimethylcarbamate, neodymiumdiethylcarbamate, neodymium diisopropylcarbamate, neodymiumdibutylcarbamate, or neodymium dibenzylcarbamate); dithiocarbamatescontaining the above-described rare earth element (e.g., neodymiumdimethyldithiocarbamate, neodymium diethyldithiocarbamate, neodymiumdiisopropyldithiocarbamate, or neodymium dibutyldithiocarbamate);xanthates containing the above-described rare earth element (e.g.,neodymium methylxanthate, neodymium ethylxanthate, neodymiumisopropylxanthate, neodymium butylxanthate, or neodymiumbenzylxanthate); R-diketonates containing the above-described rare earthelement (e.g., neodymium acetylacetonate, neodymiumtrifluoroacetylacetonate, neodymium hexafluoroacetylacetonate, orneodymium benzoylacetonate); alkoxides or aryloxides containing theabove-described rare earth element (e.g., neodymium methoxide, neodymiumethoxide, neodymium isopropoxide, neodymium phenoxide, or neodymiumnonylphenoxide); halides or pseudo-halides containing theabove-described rare earth element (e.g., neodymium fluoride, neodymiumchloride, neodymium bromide, neodymium iodide, neodymium cyanide,neodymium cyanate, neodymium thiocyanate, or neodymium azide);oxyhalides containing the above-described rare earth element (e.g.,neodymium oxyfluoride, neodymium oxychloride, or neodymium oxybromide);or organolanthanide rare earth element-containing compounds including atleast one rare earth element-carbon bond (e.g., Cp₃Ln, Cp₂LnR, Cp₂LnCl,CpLnCl₂, CpLn (cyclooctatetraene), (C₅Me₅)₂LnR, LnR₃, Ln(allyl)₃, orLn(allyl)₂Cl, where Ln represents a rare earth metal element, and Rrepresents a hydrocarbyl group), and may include any one thereof or amixture of two or more thereof.

Specifically, the lanthanide rare earth element-containing compound mayinclude a neodymium-based compound represented by Formula 5 below.

In Formula 5, R_(a) to R_(c) may each independently be hydrogen or analkyl group having 1 to 12 carbon atoms, but all of R_(a) to R_(c) arenot hydrogen at the same time.

As a specific example, the neodymium-based compound may be at least oneselected from the group consisting of Nd(neodecanoate)₃,Nd(2-ethylhexanoate)₃, Nd(2,2-diethyl decanoate)₃, Nd(2,2-dipropyldecanoate)₃, Nd(2,2-dibutyl decanoate)₃, Nd(2,2-dihexyl decanoate)₃,Nd(2,2-dioctyl decanoate)₃, Nd(2-ethyl-2-propyl decanoate)₃,Nd(2-ethyl-2-butyl decanoate)₃, Nd(2-ethyl-2-hexyl decanoate)₃,Nd(2-propyl-2-butyl decanoate)₃, Nd (2-propyl-2-hexyl decanoate)₃,Nd(2-propyl-2-isopropyl decanoate)₃, Nd(2-butyl-2-hexyl decanoate)₃,Nd(2-hexyl-2-octyl decanoate)₃, Nd(2-t-butyl decanoate)₃, Nd(2,2-diethyloctanoate)₃, Nd(2,2-dipropyl octanoate)₃, Nd(2,2-dibutyl octanoate)₃,Nd(2,2-dihexyl octanoate)₃, Nd(2-ethyl-2-propyl octanoate)₃,Nd(2-ethyl-2-hexyl octanoate)₃, Nd(2,2-diethyl nonanoate)₃,Nd(2,2-dipropyl nonanoate)₃, Nd(2,2-dibutyl nonanoate)₃, Nd(2,2-dihexylnonanoate)₃, Nd(2-ethyl-2-propyl nonanoate)₃, and Nd(2-ethyl-2-hexylnonanoate)₃.

As another example, in consideration of excellent solubility in thepolymerization solvent without a concern for oligomerization, a rate ofconversion to a catalytically active species, and the resultingexcellent catalytic activity improvement effect, the lanthanide rareearth element-containing compound may specifically be a neodymium-basedcompound in which, in Formula 5, R_(a) is a linear or branched alkylgroup having 4 to 12 carbon atoms, and R_(b) and R_(c) are eachindependently hydrogen or an alkyl group having 2 to 8 carbon atoms, butR_(b) and R_(c) are not hydrogen at the same time.

As a specific example, in Formula 5, R_(a) may be a linear or branchedalkyl group having 6 to 8 carbon atoms, and R_(b) and R_(c) may eachindependently be hydrogen or an alkyl group having 2 to 6 carbon atoms,wherein R_(b) and R_(c) may not be hydrogen at the same time, specificexamples of the neodymium-based compound may be at least one selectedfrom the group consisting of Nd(2,2-diethyl decanoate)₃, Nd(2,2-dipropyldecanoate)₃, Nd(2,2-dibutyl decanoate)₃, Nd(2,2-dihexyl decanoate)₃,Nd(2,2-dioctyl decanoate)₃, Nd(2-ethyl-2-propyl decanoate)₃,Nd(2-ethyl-2-butyl decanoate)₃, Nd(2-ethyl-2-hexyl decanoate)₃,Nd(2-propyl-2-butyl decanoate)₃, Nd(2-propyl-2-hexyl decanoate)₃,Nd(2-propyl-2-isopropyl decanoate)₃, Nd(2-butyl-2-hexyl decanoate)₃,Nd(2-hexyl-2-octyl decanoate)₃, Nd(2-t-butyl decanoate)₃, Nd(2,2-diethyloctanoate)₃, Nd(2,2-dipropyl octanoate)₃, Nd(2,2-dibutyl octanoate)₃,Nd(2,2-dihexyl octanoate)₃, Nd(2-ethyl-2-propyl octanoate)₃,Nd(2-ethyl-2-hexyl octanoate)₃, Nd(2,2-diethyl nonanoate)₃,Nd(2,2-dipropyl nonanoate)₃, Nd(2,2-dibutyl nonanoate)₃, Nd(2,2-dihexylnonanoate)₃, Nd(2-ethyl-2-propyl nonanoate)₃, and Nd(2-ethyl-2-hexylnonanoate)₃, and, among them, the neodymium-based compound may be atleast one selected from the group consisting of Nd(2,2-diethyldecanoate)₃, Nd(2,2-dipropyl decanoate)₃, Nd(2,2-dibutyl decanoate)₃,Nd(2,2-dihexyl decanoate)₃, and Nd(2,2-dioctyl decanoate)₃.

Specifically, in Formula 5, R_(a) may be a linear or branched alkylgroup having 6 to 8 carbon atoms, and R_(b) and R_(c) may eachindependently be an alkyl group having 2 to 6 carbon atoms.

As described above, since the neodymium-based compound represented byFormula 5 includes a carboxylate ligand including alkyl groups ofvarious lengths having 2 or more carbon atoms as a substituent at an a(alpha) position, coagulation of the compound may be blocked by inducingsteric changes around the neodymium center metal, and accordingly,oligomerization may be suppressed. Also, with respect to theneodymium-based compound, since a ratio of neodymium located in a centerportion, which has high solubility in the polymerization solvent and hasdifficulties in conversion to the catalytically active species, isreduced, the rate of conversion to the catalytically active species ishigh.

Furthermore, the lanthanide rare earth element-containing compoundaccording to an embodiment of the present invention may have asolubility of about 4 g or more per 6 g of a non-polar solvent at roomtemperature (25° C.).

In the present invention, the solubility of the neodymium-based compounddenotes a degree to which the neodymium-based compound is clearlydissolved without a turbidity phenomenon, wherein since theneodymium-based compound has high solubility as described above,excellent catalytic activity may be achieved.

Also, the lanthanide rare earth element-containing compound according tothe embodiment of the present invention may be used in the form of areactant with a Lewis base. The reactant may improve the solubility ofthe lanthanide rare earth element-containing compound in the solvent andmay be stored in a stable state for a long period of time by the Lewisbase. The Lewis base, for example, may be used in a ratio of 30 mol orless or 1 mole to 10 mol per 1 mol of the rare earth element. Examplesof the Lewis base may be acetylacetone, tetrahydrofuran, pyridine,N,N′-dimethylformamide, thiophene, diphenyl ether, triethylamine, anorganic phosphorus compound, or a monohydric or dihydric alcohol.

The catalyst composition may further include at least one of (a)alkylating agent, (b) halide, and (c) conjugated diene-based monomer, inaddition to the lanthanide rare earth element-containing compound.

Hereinafter, (a) alkylating agent, (b) halide, and (c) conjugateddiene-based monomer will be separately described in detail.

(a) Alkylating Agent

The alkylating agent is an organometallic compound that may transfer ahydrocarbyl group to another metal, wherein it may act as a cocatalystcomposition. The alkylating agent may be used without particularlimitation as long as it is commonly used as an alkylating agent duringthe preparation of a diene-based polymer, and, for example, may be anorganometallic compound, which is soluble in the polymerization solventand contains a metal-carbon bond, such as an organoaluminum compound, anorganomagnesium compound, or an organolithium compound.

Specifically, the organoaluminum compound may include alkylaluminum suchas trimethylaluminum, triethylaluminum, tri-n-propylaluminum,triisopropylaluminum, tri-n-butylaluminum, triisobutylaluminum,tri-t-butylaluminum, tripentylaluminum, trihexylaluminum,tricyclohexylaluminum, or trioctylaluminum; dihydrocarbylaluminumhydride such as diethylaluminum hydride, di-n-propylaluminum hydride,diisopropylaluminum hydride, di-n-butylaluminum hydride,diisobutylaluminum hydride (DIBAH), di-n-octylaluminum hydride,diphenylaluminum hydride, di-p-tolylaluminum hydride, dibenzylaluminumhydride, phenylethylaluminum hydride, phenyl-n-propylaluminum hydride,phenylisopropylaluminum hydride, phenyl-n-butylaluminum hydride,phenylisobutylaluminum hydride, phenyl-n-octylaluminum hydride,p-tolylethylaluminum hydride, p-tolyl-n-propylaluminum hydride,p-tolylisopropylaluminum hydride, p-tolyl-n-butylaluminum hydride,p-tolylisobutylaluminum hydride, p-tolyl-n-octylaluminum hydride,benzylethylaluminum hydride, benzyl-n-propylaluminum hydride,benzylisopropylaluminum hydride, benzyl-n-butylaluminum hydride,benzylisobutylaluminum hydride, or benzyl-n-octylaluminum hydride; andhydrocarbylaluminum dihydride such as ethylaluminum dihydride,n-propylaluminum dihydride, isopropylaluminum dihydride, n-butylaluminumdihydride, isobutylaluminum dihydride, or n-octylaluminum dihydride. Theorganomagnesium compound may include an alkyl magnesium compound such asdiethylmagnesium, di-n-propylmagnesium, diisopropylmagnesium,dibutylmagnesium, dihexylmagnesium, diphenylmagnesium, ordibenzylmagnesium, and the organolithium compound may include an alkyllithium compound such as n-butyllithium.

Also, the organoaluminum compound may be aluminoxane.

The aluminoxane may be prepared by reacting atrihydrocarbylaluminum-based compound with water, and may specificallybe linear aluminoxane of the following Formula 6a or cyclic aluminoxaneof the following Formula 6b.

In Formulae 6a and 6b, R is a monovalent organic group bonded to analuminum atom through a carbon atom, wherein R may be a hydrocarbylgroup, and x and y may each independently be an integer of 1 or more,particularly 1 to 100, and more particularly 2 to 50.

For example, the aluminoxane may include methylaluminoxane (MAO),modified methylaluminoxane (MMAO), ethylaluminoxane,n-propylaluminoxane, isopropylaluminoxane, butylaluminoxane,isobutylaluminoxane, n-pentylaluminoxane, neopentylaluminoxane,n-hexylaluminoxane, n-octylaluminoxane, 2-ethylhexylaluminoxane,cylcohexylaluminoxane, 1-methylcyclopentylaluminoxane,phenylaluminoxane, or 2,6-dimethylphenylaluminoxane, and any one thereofor a mixture of two or more thereof may be used.

Furthermore, the modified methylaluminoxane may be one in which a methylgroup of methylaluminoxane is substituted with a formula group (R),specifically, a hydrocarbon group having 2 to 20 carbon atoms, whereinthe modified methylaluminoxane may specifically be a compoundrepresented by Formula 7 below.

In Formula 7, R is the same as defined above, and m and n may eachindependently be an integer of 2 or more. Also, in Formula 7, Merepresents a methyl group.

Specifically, in Formula 7, R may be an alkyl group having 2 to 20carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an alkenylgroup having 2 to 20 carbon atoms, a cycloalkenyl group having 3 to 20carbon atoms, an aryl group having 6 to 20 carbon atoms, an arylalkylgroup having 7 to 20 carbon atoms, an alkylaryl group having 7 to 20carbon atoms, an allyl group, or an alkynyl group having 2 to 20 carbonatoms, may particularly be an alkyl group having 2 to 10 carbon atomssuch as an ethyl group, an isobutyl group, a hexyl group, or an octylgroup, and may more particularly be an isobutyl group.

Specifically, the modified methylaluminoxane may be one in which about50 mol % to 90 mol % of the methyl group of the methylaluminoxane issubstituted with the above-described hydrocarbon group. When the amountof the hydrocarbon group substituted in the modified methylaluminoxaneis within the above range, the modified methylaluminoxane may increasecatalytic activity by promoting alkylation.

The modified methylaluminoxane may be prepared by a conventional method,and may specifically be prepared by using trimethylaluminum andalkylaluminum other than trimethylaluminum. In this case, thealkylaluminum may be triisopropylaluminum, triethylaluminum,trihexylaluminum, or trioctylaluminum, and any one thereof or a mixtureof two or more thereof may be used.

Also, the catalyst composition according to an embodiment of the presentinvention may include the alkylating agent at a molar ratio of 1 to 200,particularly 1 to 100, and more particularly 3 to 20 based on 1 mol ofthe lanthanide rare earth element-containing compound. In a case inwhich the alkylating agent is included at a molar ratio of greater than200, catalytic reaction control is not easy during the preparation ofthe polymer, and an excessive amount of the alkylating agent may cause aside reaction.

(b) Halide

The halide is not particularly limited, but, for example, may includeelemental halogen, an interhalogen compound, halogenated hydrogen, anorganic halide, a non-metal halide, a metal halide, or an organic metalhalide, and any one thereof or a mixture of two or more thereof may beused. Among them, in consideration of catalytic activity enhancement andthe resulting significant improvement in reactivity, any one selectedfrom the group consisting of an organic halide, a metal halide, and anorganic metal halide, or a mixture of two or more thereof may be used asthe halide.

The elemental halogen may include fluorine, chlorine, bromine, oriodine.

Also, the interhalogen compound may include iodine monochloride, iodinemonobromide, iodine trichloride, iodine pentafluoride, iodinemonofluoride, or iodine trifluoride.

Furthermore, the halogenated hydrogen may include hydrogen fluoride,hydrogen chloride, hydrogen bromide, or hydrogen iodide.

Also, the organic halide may include t-butyl chloride (t-BuCl), t-butylbromide, allyl chloride, allyl bromide, benzyl chloride, benzyl bromide,chloro-di-phenylmethane, bromo-di-phenylmethane, triphenylmethylchloride, triphenylmethyl bromide, benzylidene chloride, benzylienebromide, methyltrichlorosilane, phenyltrichlorosilane,dimethyldichlorosilane, diphenyldichlorosilane, trimethylchlorosilane(TMSCl), benzoyl chloride, benzoyl bromide, propionyl chloride,propionyl bromide, methyl chloroformate, methyl bromoformate,iodomethane, diiodomethane, triiodomethane (also referred to as‘iodoform’), tetraiodomethane, 1-iodopropane, 2-iodopropane,1,3-diiodopropane, t-butyl iodide, 2,2-dimethyl-1-iodopropane (alsoreferred to as ‘neopentyl iodide’), allyl iodide, iodobenzene, benzyliodide, diphenylmethyl iodide, triphenylmethyl iodide, benzylideneiodide (also referred to as ‘benzal iodide’), trimethylsilyl iodide,triethylsilyl iodide, triphenylsilyl iodide, dimethyldiiodosilane,diethyldiiodosilane, diphenyldiiodosilane, methyltriiodosilane,ethyltriiodosilane, phenyltriiodosilane, benzoyl iodide, propionyliodide, or methyl iodoformate.

Furthermore, the non-metal halide may include phosphorous trichloride,phosphorous tribromide, phosphorous pentachloride, phosphorousoxychloride, phosphorous oxybromide, boron trifluoride, borontrichloride, boron tribromide, silicon tetrafluoride, silicontetrachloride (SiCl₄), silicon tetrabromide, arsenic trichloride,arsenic tribromide, selenium tetrachloride, selenium tetrabromide,tellurium tetrachloride, tellurium tetrabromide, silicon tetraiodide,arsenic triiodide, tellurium tetraiodide, boron triiodide, phosphoroustriiodide, phosphorous oxyiodide, or selenium tetraiodide.

Also, the metal halide may include tin tetrachloride, tin tetrabromide,aluminum trichloride, aluminum tribromide, antimony trichloride,antimony pentachloride, antimony tribromide, aluminum trifluoride,gallium trichloride, gallium tribromide, gallium trifluoride, indiumtrichloride, indium tribromide, indium trifluoride, titaniumtetrachloride, titanium tetrabromide, zinc dichloride, zinc dibromide,zinc difluoride, aluminum triiodide, gallium triiodide, indiumtriiodide, titanium tetraiodide, zinc diiodide, germanium tetraiodide,tin tetraiodide, tin diiodide, antimony triiodide, or magnesiumdiiodide.

Furthermore, the organic metal halide may include dimethylaluminumchloride, diethylaluminum chloride, dimethylaluminum bromide,diethylaluminum bromide, dimethylaluminum fluoride, diethylaluminumfluoride, methylaluminum dichloride, ethylaluminum dichloride,methylaluminum dibromide, ethylaluminum dibromide, methylaluminumdifluoride, ethylaluminum difluoride, methylaluminum sesquichloride,ethylaluminum sesquichloride (EASC), isobutylaluminum sesquichloride,methylmagnesium chloride, methylmagnesium bromide, ethylmagnesiumchloride, ethylmagnesium bromide, n-butylmagnesium chloride,n-butylmagnesium bromide, phenylmagnesium chloride, phenylmagnesiumbromide, benzylmagnesium chloride, trimethyltin chloride, trimethyltinbromide, triethyltin chloride, triethyltin bromide, di-t-butyltindichloride, di-t-butyltin dibromide, di-n-butyltin dichloride,di-n-butyltin dibromide, tri-n-butyltin chloride, tri-n-butyltinbromide, methylmagnesium iodide, dimethylaluminum iodide,diethylaluminum iodide, di-n-butylaluminum iodide, diisobutylaluminumiodide, di-n-octylaluminum iodide, methylaluminum diiodide,ethylaluminum diiodide, n-butylaluminum diiodide, isobutylaluminumdiiodide, methylaluminum sesquiiodide, ethylaluminum sesquiiodide,isobutylaluminum sesquiiodide, ethylmagnesium iodide, n-butylmagnesiumiodide, isobutylmagnesium iodide, phenylmagnesium iodide,benzylmagnesium iodide, trimethyltin iodide, triethyltin iodide,tri-n-butyltin iodide, di-n-butyltin diiodide, or di-t-butyl tindiiodide.

Also, the catalyst composition according to the embodiment of thepresent invention may include the halide in an amount of 1 mol to 20mol, particularly 1 mol to 5 mol, and more particularly 2 mol to 3 molbased on 1 mol of the lanthanide rare earth element-containing compound.In a case in which the halide is included in an amount of greater than20 mol, catalytic reaction control is not easy and an excessive amountof the halide may cause a side reaction.

Furthermore, the catalyst composition for preparing a conjugated dienepolymer according to the embodiment of the present invention may includea non-coordinating anion-containing compound or a non-coordinating anionprecursor compound instead of the halide or with the halide.

Specifically, in the compound containing a non-coordinating anion, thenon-coordinating anion is a sterically bulky anion that does not form acoordinate bond with an active center of a catalyst system due to sterichindrance, wherein the non-coordinating anion may be a tetraarylborateanion or a fluorinated tetraarylborate anion. Also, the compoundcontaining a non-coordinating anion may include a counter cation, forexample, a carbonium cation such as a triarylcarbonium cation; anammonium cation, such as N,N-dialkyl anilinium cation, or a phosphoniumcation, in addition to the above-described non-coordinating anion. Forexample, the compound containing a non-coordinating anion may includetriphenylcarbonium tetrakis(pentafluorophenyl)borate,N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate,triphenylcarbonium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, orN,N-dimethylanilinium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate.

Also, the non-coordinating anion precursor, as a compound capable offorming a non-coordinating anion under the reaction conditions, mayinclude a triaryl boron compound (BE₃, where E is a strongelectron-withdrawing aryl group such as a pentafluorophenyl group or3,5-bis(trifluoromethyl)phenyl group).

(c) Conjugated Diene-Based Monomer

Also, the catalyst composition may further include a conjugateddiene-based monomer, and, since the catalyst composition is used in theform of a performing catalyst composition in which a portion of theconjugated diene-based monomer used in the polymerization reaction ispre-polymerized by being premixed with the catalyst composition forpolymerization, catalyst composition activity may not only be improved,but a conjugated diene-based polymer thus prepared may be stabilized.

In the present invention, the expression “preforming” may denote that,in a case in which a catalyst composition including a lanthanide rareearth element-containing compound, an alkylating agent, and a halide,that is, a catalyst system includes diisobutylaluminum hydride (DIBAH),a small amount of a conjugated diene-based monomer, such as1,3-butadiene, is added to reduce the possibility of producing variouscatalytically active species, and pre-polymerization is performed in thecatalyst composition system with the addition of the 1,3-butadiene.Also, the expression “premix” may denote a state in which each compoundis uniformly mixed in the catalyst composition system without beingpolymerized.

In this case, with respect to the conjugated diene-based monomer used inthe preparation of the catalyst composition, some amount within a totalamount range of the conjugated diene-based monomer used in thepolymerization reaction may be used, and, for example, the conjugateddiene-based monomer may be used in an amount of 1 mol to 100 mol, forexample, 10 mol to 50 mol, or 20 mol to 50 mol based on 1 mol of thelanthanide rare earth element-containing compound.

The catalyst composition according to the embodiment of the presentinvention may be prepared by sequentially mixing the above-describedlanthanide rare earth element-containing compound and at least one ofthe alkylating agent, the halide, and the conjugated diene-basedmonomer, specifically, the lanthanide rare earth element-containingcompound, alkylating agent, halide, and selectively conjugateddiene-based monomer, in an organic solvent. In this case, the organicsolvent may be a non-polar solvent that is not reactive with theabove-described catalyst components. Specifically, the non-polar solventmay include linear, branched, or cyclic aliphatic hydrocarbon having 5to 20 carbon atoms such as n-pentane, n-hexane, n-heptane, n-octane,n-nonane, n-decane, isopentane, isohexane, isoheptane, isooctane,2,2-dimethylbutane, cyclopentane, cyclohexane, methylcyclopentane, ormethylcyclohexane; a mixed solvent of aliphatic hydrocarbon having 5 to20 carbon atoms such as petroleum ether or petroleum spirits, orkerosene; or an aromatic hydrocarbon-based solvent such as benzene,toluene, ethylbenzene, and xylene, and any one thereof or a mixture oftwo or more thereof may be used. The non-polar solvent may morespecifically include the above-described linear, branched, or cyclicaliphatic hydrocarbon having 5 to 20 carbon atoms or the above-describedmixed solvent of aliphatic hydrocarbon, and, for example, may includen-hexane, cyclohexane, or a mixture thereof.

Also, the organic solvent may be appropriately selected depending on atype of the constituent material constituting the catalyst composition,particularly, the alkylating agent.

Specifically, since alkylaluminoxane, such as methylaluminoxane (MAO) orethylaluminoxane, as the alkylating agent, is not easily dissolved in analiphatic hydrocarbon-based solvent, an aromatic hydrocarbon-basedsolvent may be appropriately used.

Furthermore, in a case in which modified methylaluminoxane is used asthe alkylating agent, an aliphatic hydrocarbon-based solvent may beappropriately used. In this case, since a single solvent system may berealized with an aliphatic hydrocarbon-based solvent, such as hexane,mainly used as a polymerization solvent, it may be more advantageous tothe polymerization reaction. Also, the aliphatic hydrocarbon-basedsolvent may promote catalytic activity, and may further improvereactivity by the catalytic activity.

The organic solvent may be used in an amount of 20 mol to 20,000 mol,for example, 100 mol to 1,000 mol, based on 1 mol of the lanthanide rareearth element-containing compound.

The polymerization of step 1 may be performed by coordination anionicpolymerization or radical polymerization, may specifically be bulkpolymerization, solution polymerization, suspension polymerization, oremulsion polymerization, and, for example, may be solutionpolymerization.

Also, the polymerization may be performed by any method of batch andcontinuous methods. Specifically, the polymerization of step 1 may beperformed by adding the conjugated diene-based monomer to the catalystcomposition and performing a reaction in the organic solvent.

Herein, the organic solvent may be further added in addition to theamount of the organic solvent which may be used in the preparation ofthe catalyst composition, and specific types thereof may be the same asdescribed above. Also, when the organic solvent is used, a concentrationof the monomer may be in a range of 3 wt % to 80 wt %, or 10 wt % to 30wt %.

Also, during the polymerization, an additive, for example, a reactionterminating agent for the completion of the polymerization reaction,such as polyoxyethylene glycol phosphate; or an antioxidant, such as2,6-di-t-butylparacresol, may be further used. In addition, an additivethat usually facilitates solution polymerization, specifically, anadditive, such as a chelating agent, a dispersant, a pH adjuster, adeoxidizer, or an oxygen scavenger, may be further selectively used.

Furthermore, the polymerization may be temperature rise polymerization,isothermal polymerization, or constant temperature polymerization(adiabatic polymerization).

Herein, the constant temperature polymerization denotes a polymerizationmethod including a step of performing polymerization not by randomlyapplying heat but with its own reaction heat after the organometalliccompound is added, the temperature rise polymerization denotes apolymerization method in which the temperature is increased by randomlyapplying heat after the organometallic compound is added, and theisothermal polymerization denotes a polymerization method in which thetemperature of the polymer is constantly maintained by taking away heator applying heat after the organometallic compound is added.

The polymerization may be performed in a temperature range of −20° C. to200° C., particularly in a temperature range of 20° C. to 150° C., andmore particularly in a temperature range of 10° C. to 120° C. for 15minutes to 3 hours. In a case in which the temperature during thepolymerization is greater than 200° C., it is difficult to sufficientlycontrol the polymerization reaction and the cis-1,4 bond content of theformed diene-based polymer may be decreased, and, in a case in which thetemperature is less than −20° C., polymerization rate and efficiency maybe reduced.

Step 2 is a step of reacting the active polymer with the modifierrepresented by Formula 1, in order to prepare a conjugated diene-basedpolymer.

The modifier represented by Formula 1 may be the same as describedabove, and at least one type thereof may be mixed and used in thereaction.

The modifier represented by Formula 1 may be used in an amount of 0.5mol to 20 mol based on 1 mol of the lanthanide rare earthelement-containing compound in the catalyst composition. Specifically,the modifier represented by Formula 1 may be used in an amount of 1 molto 10 mol based on 1 mol of the lanthanide rare earth element-containingcompound in the catalyst composition. Since the optimal modificationreaction may be performed when the modifier is used in an amount thatsatisfies the above range, a conjugated diene-based polymer having ahigh modification ratio may be obtained.

The reaction of step 2 is a modification reaction for the introductionof a functional group into the polymer, wherein the reaction may beperformed in a temperature range of 0° C. to 90° C. for 1 minute to 5hours.

Also, the method of preparing a modified conjugated diene-based polymeraccording to the embodiment of the present invention may be performed bya batch polymerization method or a continuous polymerization methodincluding one or more reactors.

After the completion of the above-described modification reaction, thepolymerization reaction may be stopped by adding an isopropanol solutionof 2,6-di-t-butyl-p-cresol (BHT) to a polymerization reaction system.Thereafter, a modified conjugated diene-based polymer may be obtainedthrough a desolvation treatment, such as steam stripping in which apartial pressure of the solvent is reduced by supplying water vapor, ora vacuum drying treatment. Also, in addition to the above-describedmodified conjugated diene-based polymer, an unmodified active polymermay be included in a reaction product obtained as a result of theabove-described modification reaction.

The preparation method according to the embodiment of the presentinvention may further include at least one step of recovering solventand unreacted monomer and drying, if necessary, after step 2.

Furthermore, the present invention provides a rubber compositionincluding the above modified conjugated diene-based polymer and a moldedarticle prepared from the rubber composition.

The rubber composition according to an embodiment of the presentinvention may include the modified conjugated diene-based polymer in anamount of 0.1 wt % or more to 100 wt % or less, particularly 10 wt % to100 wt %, and more particularly 20 wt % to 90 wt %. In a case in whichthe amount of the modified conjugated diene-based polymer is less than0.1 wt %, an effect of improving abrasion resistance and crackresistance of a molded article prepared by using the rubber composition,for example, a tire, may be insignificant.

Also, the rubber composition may further include other rubbercomponents, if necessary, in addition to the modified conjugateddiene-based polymer, and, in this case, the rubber component may beincluded in an amount of 90 wt % or less based on a total weight of therubber composition. Specifically, the rubber component may be includedin an amount of 1 part by weight to 900 parts by weight based on 100parts by weight of the modified conjugated diene-based polymer.

The rubber component may be a natural rubber or a synthetic rubber, and,for example, the rubber component may be a natural rubber (NR) includingcis-1,4-polyisoprene; a modified natural rubber, such as an epoxidizednatural rubber (ENR), a deproteinized natural rubber (DPNR), and ahydrogenated natural rubber, in which the general natural rubber ismodified or purified; and a synthetic rubber such as a styrene-butadienerubber (SBR), polybutadiene (BR), polyisoprene (IR), a butyl rubber(IIR), an ethylene-propylene copolymer, polyisobutylene-co-isoprene,neoprene, poly(ethylene-co-propylene), poly(styrene-co-butadiene),poly(styrene-co-isoprene), poly(styrene-co-isoprene-co-butadiene),poly(isoprene-co-butadiene), poly(ethylene-co-propylene-co-diene), apolysulfide rubber, an acrylic rubber, an urethane rubber, a siliconrubber, an epichlorohydrin rubber, a butyl rubber, and a halogenatedbutyl rubber. Any one thereof or a mixture of two or more thereof may beused.

Furthermore, the rubber composition may include 0.1 part by weight to150 parts by weight of a filler based on 100 parts by weight of themodified conjugated diene-based polymer, and the filler may include asilica-based filler, a carbon black-based filler, or a combinationthereof. Specifically, the filler may be carbon black.

The carbon black-based filler is not particularly limited, but, forexample, may have a nitrogen surface area per gram (N₂SA, measuredaccording to JIS K 6217-2:2001) of 20 m²/g to 250 m²/g. Also, the carbonblack may have a dibutyl phthalate (DBP) oil absorption of 80 cc/100 gto 200 cc/100 g. If the nitrogen surface area per gram of the carbonblack is greater than 250 m²/g, processability of the rubber compositionmay be reduced, and, if the nitrogen surface area per gram of the carbonblack is less than 20 m²/g, reinforcement by carbon black may beinsignificant. Furthermore, if the DBP oil absorption of the carbonblack is greater than 200 cc/100 g, the processability of the rubbercomposition may be reduced, and, if the DBP oil absorption of the carbonblack is less than 80 cc/100 g, the reinforcement by carbon black may beinsignificant.

Also, the silica-based filler is not particularly limited, but, forexample, may include wet silica (hydrous silicic acid), dry silica(anhydrous silicic acid), calcium silicate, aluminum silicate, orcolloidal silica. Specifically, the silica-based filler may be wetsilica in which an effect of improving both fracture characteristics andwet grip is the most significant. Furthermore, the silica may have anitrogen surface area per gram (N₂SA) of 120 m²/g to 180 m²/g, and acetyltrimethylammonium bromide (CTAB) surface area per gram of 100 m²/gto 200 m²/g. If the nitrogen surface area per gram of the silica is lessthan 120 m²/g, reinforcement by silica may be insignificant, and, if thenitrogen surface area per gram of the silica is greater than 180 m²/g,the processability of the rubber composition may be reduced. Also, ifthe CTAB surface area per gram of the silica is less than 100 m²/g, thereinforcement by silica, as the filler, may be insignificant, and, ifthe CTAB surface area per gram of the silica is greater than 200 m²/g,the processability of the rubber composition may be reduced.

In a case in which silica is used as the filler, a silane coupling agentmay be used together for the improvement of reinforcement and low heatgeneration property.

Specific examples of the silane coupling agent may bebis(3-triethoxysilylpropyl)tetrasulfide,bis(3-triethoxysilylpropyl)trisulfide,bis(3-triethoxysilylpropyl)disulfide,bis(2-triethoxysilylethyl)tetrasulfide,bis(3-trimethoxysilylpropyl)tetrasulfide,bis(2-trimethoxysilylethyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyl triethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyl triethoxysilane,3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide,3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide,2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide,3-trimethoxysilylpropyl benzothiazolyl tetrasulfide,3-triethoxysilylpropyl benzolyl tetrasulfide, 3-triethoxysilylpropylmethacrylate monosulfide, 3-trimethoxysilylpropyl methacrylatemonosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide,3-mercaptopropyl dimethoxymethylsilane,dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, ordimethoxymethylsilylpropyl benzothiazolyl tetrasulfide, and any onethereof or a mixture of two or more thereof may be used. For example, inconsideration of the effect of improving the reinforcement, the silanecoupling agent may be bis(3-triethoxysilylpropyl)polysulfide or3-trimethoxysilylpropyl benzothiazyl tetrasulfide.

Furthermore, in the rubber composition according to the embodiment ofthe present invention, since the modified conjugated diene-basedpolymer, in which a function group having a high affinity with thesilica is introduced into the active site, is used as the rubbercomponent, a mixing amount of the silane coupling agent may be reducedin comparison to a conventional case. Specifically, the silane couplingagent may be used in an amount of 1 part by weight to 20 parts by weightbased on 100 parts by weight of the silica. In a case in which thesilane coupling agent is used within the above range, the silanecoupling agent may prevent gelation of the rubber component whilesufficiently having an effect as a coupling agent. For example, thesilane coupling agent may be used in an amount of 5 parts by weight to15 parts by weight based on 100 parts by weight of the silica.

Also, the rubber composition according to the embodiment of the presentinvention may be sulfur cross-linkable, and, accordingly, may furtherinclude a vulcanizing agent.

The vulcanizing agent may specifically be sulfur powder, and may beincluded in an amount of 0.1 part by weight to 10 parts by weight basedon 100 parts by weight of the rubber component. When the vulcanizingagent is included within the above range, elastic modulus and strengthrequired for the vulcanized rubber composition may be secured and,simultaneously, a low fuel consumption property may be obtained.

Furthermore, the rubber composition according to the embodiment of thepresent invention may further include various additives, such as avulcanization accelerator, process oil, a plasticizer, an antioxidant, ascorch inhibitor, zinc white, stearic acid, a thermosetting resin, or athermoplastic resin, used in the general rubber industry, in addition tothe above-described components.

The vulcanization accelerator is not particularly limited, but,specifically, a thiazole-based compound, such as 2-mercaptobenzothiazole(M), dibenzothiazyl disulfide (DM), andN-cyclohexylbenzothiazole-2-sulfenamide (CZ), or a guanidine-basedcompound, such as diphenylguanidine (DPG), may be used. Thevulcanization accelerator may be included in an amount of 0.1 part byweight to 5 parts by weight based on 100 parts by weight of the rubbercomponent.

Also, the process oil acts as a softener in the rubber composition,wherein the process oil may be a paraffin-based, naphthenic-based, oraromatic-based compound, and, for example, the aromatic-based compoundmay be used in consideration of tensile strength and abrasionresistance, and the naphthenic-based or paraffin-based process oil maybe used in consideration of hysteresis loss and low temperaturecharacteristics. The process oil may be included in an amount of 100parts by weight or less based on 100 parts by weight of the rubbercomponent, and, when the process oil is included in the above amount,decreases in tensile strength and low heat generation property (low fuelconsumption property) of the vulcanized rubber may be prevented.

Furthermore, specific examples of the antioxidant may beN-isopropyl-N′-phenyl-p-phenylenediamine,N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine,6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, or a high-temperaturecondensate of diphenylamine and acetone. The antioxidant may be used inan amount of 0.1 part by weight to 6 parts by weight based on 100 partsby weight of the rubber component.

The rubber composition according to the embodiment of the presentinvention may be obtained by kneading the above mixing formulation usinga kneader such as a Banbury mixer, a roll, and an internal mixer, and arubber composition having excellent abrasion resistance as well as lowheat generation property may also be obtained by a vulcanization processafter molding.

Accordingly, the rubber composition may be suitable for the preparationof each member of a tire, such as a tire's tread, an under tread, asidewall, a carcass coating rubber, a belt coating rubber, a beadfiller, a chafer, or a bead coating rubber, or various industrial rubberproducts such as an anti-vibration rubber, a belt conveyor, and a hose.

The molded article prepared by using the rubber composition may includea tire or a tire's tread.

Hereinafter, the present invention will be described in more detail,according to specific examples and experimental examples. However, thefollowing examples and experimental examples are merely presented toexemplify the present invention, and the scope of the present inventionis not limited thereto.

Preparation Example 1: Preparation of Modifier Represented by Formula1-1

1) Preparation of Ethyl 6-Aminohexanoate Hydrochloride

After 240.0 g (1.83 mol) of 6-aminohexanoic acid was put in a 2 Lround-bottom flask and 80 ml of ethanol was added thereto, thetemperature was set at 0° C. Thereafter, a reaction was performed while126.77 ml (1.74 mol) of thionyl chloride was slowly added for 30minutes. When the exothermic process ended, a reaction was performed atroom temperature for 12 hours or more, the reaction was then terminated,and the solvent was removed under reduced pressure. After 1 L ofn-hexane was put and stirred for 30 minutes, the solution was filtered.After 1 L of diethyl ether was put, secondary stirring was performed,and the solution thus obtained was filtered and then concentrated toobtain 347.4 g (yield: 97%) of ethyl 6-aminohexanoate hydrochloride. ¹Hnuclear magnetic resonance spectroscopic data of the ethyl6-aminohexanoate hydrochloride are as follows.

¹H-NMR (500 MHz, CDCl₃) δ 8.30 (s, 3H), 4.14-4.10 (q, 2H), 3.03-3.00 (t,2H), 2.33-2.30 (t, 2H), 1.82-1.79 (t, 2H), 1.68-1.65 (t, 2H), 1.47-1.44(t, 2H), 1.26-1.23 (t, 3H).

2) Preparation of Ethyl 6-Aminohexanoate

After 340.0 g (1.74 mol) of the ethyl 6-aminohexanoate hydrochlorideprepared in 1) was put in a 2 L round-bottom flask and 700 ml ofdichloromethane was added thereto, the temperature was set at 0° C.Thereafter, a reaction was performed for 12 hours by slowly increasingthe temperature to room temperature while 605.86 ml (4.34 mol) oftriethylamine was slowly added for 30 minutes, and the reaction was thenterminated. After 500 ml of water was added to extract an organic layer,sodium sulfate was added to the organic layer, filtered, and thenconcentrated to obtain 273.7 g (yield: 98.9%) of ethyl 6-aminohexanoate.1H nuclear magnetic resonance spectroscopic data of the ethyl6-aminohexanoate are as follows.

¹H-NMR (500 MHz, CDCl₃) δ 4.13-4.09 (q, 2H), 2.69-2.67 (t, 2H),2.30-2.27 (t, 2H), 1.60 (m, 2H), 1.48-1.42 (m, 2H), 1.37-1.31 (m, 2H),1.25-1.23 (t, 2H), 1.19 (s, 3H).

3) Preparation of Modifier Represented by Formula 1-1

After 170.0 g (1.07 mol) of the ethyl 6-aminohexanoate prepared in 2)was put in a 1 L round-bottom flask and 267 ml (2.14 mol) of methylisobutyl ketone was added thereto, a reaction was performed for 12 hoursby increasing the temperature to 135° C. using a Dean-Stark apparatus,and the reaction was then terminated. The remaining methyl isobutylketone was removed to prepare 240.3 g (yield: 93.2%) of a compoundrepresented by Formula 1-1 below. ¹H nuclear magnetic resonancespectroscopic data of Formula 1-1 are as follows.

¹H-NMR (500 MHz, CDCl₃) δ 4.13-4.09 (q, 2H), 3.23-3.20 (t, 2H),2.31-2.29 (t, 2H), 2.12-2.10 (m, 2H), 1.77 (s, 3H), 1.69-1.61 (m, 4H),1.40-1.34 (m, 2H), 1.26-1.23 (t, 2H), 0.92-0.88 (m, 6H).

Preparation Example 2: Preparation of Modifier Represented by Formula1-2

1) Preparation of Ethyl 11-Aminoundecanoate Hydrochloride

After 30.0 g (149.02 mmol) of 11-aminoundecanoic acid was put in a 250mL round-bottom flask and 100 ml of ethanol was added thereto, thetemperature was set at 0° C. Thereafter, a reaction was performed while10.33 ml (141.57 mmol) of thionyl chloride was slowly added for 30minutes. When the exothermic process ended, a reaction was performed atroom temperature for 12 hours or more, the reaction was then terminated,and the solvent was removed under reduced pressure. After 500 mL ofn-hexane was put and stirred for 30 minutes, the solution was filtered.After 500 mL of diethyl ether was put, secondary stirring was performed,and the solution thus obtained was filtered and then concentrated toobtain 38.4 g (yield: 97%) of ethyl 11-aminoundecanoate hydrochloride.¹H nuclear magnetic resonance spectroscopic data of the ethyl11-aminoundecanoate hydrochloride are as follows.

¹H-NMR (500 MHz, CDCl₃) δ 8.32 (s, 3H), 4.14-4.10 (q, 2H), 3.99-2.96 (t,2H), 2.30-2.27 (t, 2H), 1.79-1.73 (m, 2H), 1.62-1.58 (m, 2H), 1.39-1.37(m, 2H), 1.28-1.24 (t, 13H).

2) Preparation of Ethyl 11-Aminoundecanoate

After 36.6 g (137.69 mmol) of the ethyl 11-aminoundecanoatehydrochloride prepared in 1) was put in a 250 mL round-bottom flask and100 ml of dichloromethane was added thereto, the temperature was set at0° C. Thereafter, a reaction was performed for 12 hours by slowlyincreasing the temperature to room temperature while 28.81 ml (206.53mmol) of triethylamine was slowly added for 30 minutes, and the reactionwas then terminated. After 500 ml of water was added to extract anorganic layer, sodium sulfate was added to the organic layer, filtered,and then concentrated to obtain 37.8 g (yield: 97.8%) of ethyl11-aminoundecanoate. ¹H nuclear magnetic resonance spectroscopic data ofthe ethyl 11-aminoundecanoate are as follows.

¹H-NMR (500 MHz, CDCl₃) δ 4.13-4.09 (q, 2H), 2.68-2.66 (t, 2H), 2.28 (t,2H), 1.61-1.58 (m, 2H), 1.54-1.51 (m, 2H), 1.44-1.40 (m, 2H), 1.27-1.22(m, 15H).

3) Preparation of Modifier Represented by Formula 1-2

After 30.0 g (130.80 mmol) of the ethyl 11-aminoundecanoate prepared in2) was put in a 500 mL round-bottom flask and 32.71 ml (261.92 mmol) ofmethyl isobutyl ketone was added thereto, a reaction was performed for12 hours by increasing the temperature to 135° C. using a Dean-Starkapparatus, and the reaction was then terminated. The remaining methylisobutyl ketone was removed to prepare 38.1 g (yield: 93.5%) of acompound represented by Formula 1-2 below. ¹H nuclear magnetic resonancespectroscopic data of Formula 1-2 are as follows.

¹H-NMR (500 MHz, CDCl₃) δ 4.14-4.10 (q, 2H), 3.26-3.21 (m, 2H),2.29-2.26 (t, 2H), 2.12-2.10 (m, 2H), 1.97-1.92 (m, 2H), 1.77 (s, 3H),1.63-1.56 (m, 4H), 1.27-1.23 (m, 11H), 1.26-1.23 (t, 3H), 0.93-0.87 (m,6H).

Preparation Example 3: Preparation of Modifier Represented by Formula1-3

1) Preparation of Ethyl 4-Aminobutanoate Hydrochloride

After 200.0 g (1.94 mol) of 4-aminobutanoic acid was put in a 2 Lround-bottom flask and 500 ml of ethanol was added thereto, thetemperature was set at 0° C. Thereafter, a reaction was performed while134.38 ml (1.84 mol) of thionyl chloride was slowly added for 30minutes. When the exothermic process ended, a reaction was performed atroom temperature for 12 hours or more, the reaction was then terminated,and the solvent was removed under reduced pressure. After 1 L ofn-hexane was put and stirred for 30 minutes, the solution was filtered.After 1 L of diethyl ether was put, secondary stirring was performed,and the solution thus obtained was filtered and then concentrated toobtain 315.7 g (yield: 97%) of ethyl 4-aminobutanoate hydrochloride. ¹Hnuclear magnetic resonance spectroscopic data of the ethyl4-aminobutanoate hydrochloride are as follows.

¹H-NMR (500 MHz, CDCl₃) δ 8.27 (br, s, 3H), 4.16-4.12 (q, 2H), 3.15-3.10(m, 2H), 2.52-2.50 (t, 2H), 2.12-2.10 (t, 2H), 1.24-1.25 (t, 3H).

2) Preparation of Ethyl 4-Aminobutanoate

After 300.0 g (1.79 mol) of the ethyl 4-aminobutanoate hydrochlorideprepared in 1) was put in a 2 L round-bottom flask and 600 ml ofdichloromethane was added thereto, the temperature was set at 0° C.Thereafter, a reaction was performed for 12 hours by slowly increasingthe temperature to room temperature while 374.43 ml (2.68 mol) oftriethylamine was slowly added for 30 minutes, and the reaction was thenterminated. After 500 ml of water was added to extract an organic layer,sodium sulfate was added to the organic layer, filtered, and thenconcentrated to obtain 230.6 g (yield: 98.2%) of ethyl 4-aminobutanoate.1H nuclear magnetic resonance spectroscopic data of the ethyl4-aminobutanoate are as follows.

¹H-NMR (500 MHz, CDCl₃) δ 4.13-4.09 (q, 2H), 2.68-2.66 (t, 2H),2.46-2.44 (t, 2H), 2.06-2.02 (m, 2H), 1.25-1.22 (t, 3H), 1.18 (s, 2H).

3) Preparation of Modifier Represented by Formula 1-3

After 220.0 g (1.68 mol) of the ethyl 4-aminobutanoate prepared in 2)was put in a 1 L round-bottom flask and 419.44 ml (3.35 mol) of methylisobutyl ketone was added thereto, a reaction was performed for 12 hoursby increasing the temperature to 135° C. using a Dean-Stark apparatus,and the reaction was then terminated. The remaining methyl isobutylketone was removed to prepare 335.7 g (yield: 93.8%) of a compoundrepresented by Formula 1-3 below. ¹H nuclear magnetic resonancespectroscopic data of Formula 1-3 are as follows.

¹H-NMR (500 MHz, CDCl₃) δ 4.12-4.08 (q, 2H), 3.21-3.18 (t, 2H),2.30-2.28 (t, 2H), 2.10-2.08 (m, 2H), 1.76 (s, 3H), 1.69-1.61 (m, 3H),1.25-1.22 (t, 3H), 0.92-0.88 (d, 6H).

Preparation Example 4: Preparation of Modifier Represented by Formula1-4

1) Preparation of Butyl 6-Aminohexanoate Hydrochloride

After 204.0 g (1.52 mol) of 6-aminohexanoic acid was put in a 2 Lround-bottom flask and 600 ml of n-butanol was added thereto, thetemperature was set at 0° C. Thereafter, a reaction was performed while100.15 ml (1.37 mol) of thionyl chloride was slowly added for 30minutes. When the exothermic process ended, a reaction was performed atroom temperature for 12 hours or more, the reaction was then terminated,and the solvent was removed under reduced pressure. After 1 L ofn-hexane was put and stirred for 30 minutes, the solution was filtered.After 1 L of diethyl ether was put, secondary stirring was performed,and the solution thus obtained was filtered and then concentrated toobtain 328.9 g (yield: 96.4%) of butyl 6-aminohexanoate hydrochloride.¹H nuclear magnetic resonance spectroscopic data of the butyl6-aminohexanoate hydrochloride are as follows.

¹H-NMR (500 MHz, CDCl₃) δ 8.28 (s, 3H), 4.13-4.09 (q, 2H), 3.02-2.99 (t,2H), 2.33-2.30 (t, 2H), 1.81-1.78 (t, 2H), 1.67-1.64 (t, 2H), 1.47-1.44(t, 2H), 1.34-1.31 (m, 2H), 1.25-1.22 (m, 2H), 0.94-0.91 (t, 3H).

2) Preparation of Butyl 6-Aminohexanoate

After 300.0 g (1.34 mol) of the butyl 6-aminohexanoate hydrochlorideprepared in 1) was put in a 2 L round-bottom flask and 600 ml ofdichloromethane was added thereto, the temperature was set at 0° C.Thereafter, a reaction was performed for 12 hours by slowly increasingthe temperature to room temperature while 280.34 ml (2.01 mol) oftriethylamine was slowly added for 30 minutes, and the reaction was thenterminated. After 400 ml of water was added to extract an organic layer,sodium sulfate was added to the organic layer, filtered, and thenconcentrated to obtain 244.5 g (yield: 97.4%) of butyl 6-aminohexanoate.1H nuclear magnetic resonance spectroscopic data of the butyl6-aminohexanoate are as follows.

¹H-NMR (500 MHz, CDCl₃) δ 4.14-4.10 (q, 2H), 3.03-3.00 (t, 2H),2.34-2.31 (t, 2H), 1.80-1.77 (t, 2H), 1.65-1.62 (t, 2H), 1.46-1.43 (t,2H), 1.31-1.28 (m, 2H), 1.24-1.21 (m, 2H), 1.19 (s, 2H), 0.92-0.89 (t,3H).

3) Preparation of Modifier Represented by Formula 1-4

After 220.0 g (1.17 mol) of the butyl 6-aminohexanoate prepared in 2)was put in a 1 L round-bottom flask and 293.8 ml (2.35 mol) of methylisobutyl ketone was added thereto, a reaction was performed for 12 hoursby increasing the temperature to 135° C. using a Dean-Stark apparatus,and the reaction was then terminated. The remaining methyl isobutylketone was removed to prepare 294.1 g (yield: 92.9%) of a compoundrepresented by Formula 1-4 below. ¹H nuclear magnetic resonancespectroscopic data of Formula 1-4 are as follows.

¹H-NMR (500 MHz, CDCl₃) δ 4.14-4.10 (q, 2H), 3.24-3.21 (t, 2H),2.32-2.29 (t, 2H), 2.12-2.10 (m, 2H), 1.98-1.92 (m, 2H), 1.77 (s, 3H),1.70-1.65 (m, 3H), 1.40-1.34 (m, 2H), 1.26-1.23 (t, 2H), 1.24-1.21 (m,2H), 0.92-0.84 (m, 9H).

Example 1

900 g of 1,3-butadiene and 6.6 kg of n-hexane were added to a 20 Lautoclave reactor, and an internal temperature of the reactor was thenincreased to 70° C. After a catalyst composition, which was prepared bya reaction of a hexane solution, in which 0.10 mmol of Nd(2,2-diethyldecanoate)₃ was dissolved, with 0.89 mmol of diisobutylaluminum hydride(DIBAH), 0.24 mmol of diethylaluminum chloride, and 3.3 mmol of1,3-butadiene, was added to the reactor, polymerization was performedfor 60 minutes. Thereafter, a hexane solution including 0.23 mmol of themodifier represented by Formula 1-1, which was prepared in PreparationExample 1, was added, and a modification reaction was then performed at70° C. for 30 minutes. Thereafter, a hexane solution, in which 1.0 g ofa polymerization terminator was included, and 33 g of a solution, inwhich 30 wt % of WINGSTAY (Eliokem SAS, France), as an antioxidant, wasdissolved in hexane, were added. A polymer thus obtained was put in hotwater heated by steam and stirred to remove the solvent, and was thenroll-dried to remove the remaining solvent and water to prepare amodified butadiene polymer.

Example 2

900 g of 1,3-butadiene and 6.6 kg of n-hexane were added to a 20 Lautoclave reactor, and an internal temperature of the reactor was thenincreased to 70° C. After a catalyst composition, which was prepared bya reaction of a hexane solution, in which 0.10 mmol of Nd(2,2-diethyldecanoate)₃ was dissolved, with 0.89 mmol of diisobutylaluminum hydride(DIBAH), 0.24 mmol of diethylaluminum chloride, and 3.3 mmol of1,3-butadiene, was added to the reactor, polymerization was performedfor 60 minutes. Thereafter, a hexane solution including 0.23 mmol of themodifier represented by Formula 1-2, which was prepared in PreparationExample 2, was added, and a modification reaction was then performed at70° C. for 30 minutes. Thereafter, a hexane solution, in which 1.0 g ofa polymerization terminator was included, and 33 g of a solution, inwhich 30 wt % of WINGSTAY (Eliokem SAS, France), as an antioxidant, wasdissolved in hexane, were added. A polymer thus obtained was put in hotwater heated by steam and stirred to remove the solvent, and was thenroll-dried to remove the remaining solvent and water to prepare amodified butadiene polymer.

Example 3

900 g of 1,3-butadiene and 6.6 kg of n-hexane were added to a 20 Lautoclave reactor, and an internal temperature of the reactor was thenincreased to 70° C. After a catalyst composition, which was prepared bya reaction of a hexane solution, in which 0.10 mmol of Nd(2,2-diethyldecanoate)₃ was dissolved, with 0.89 mmol of diisobutylaluminum hydride(DIBAH), 0.24 mmol of diethylaluminum chloride, and 3.3 mmol of1,3-butadiene, was added to the reactor, polymerization was performedfor 60 minutes. Thereafter, a hexane solution including 0.23 mmol of themodifier represented by Formula 1-3, which was prepared in PreparationExample 3, was added, and a modification reaction was then performed at70° C. for 30 minutes. Thereafter, a hexane solution, in which 1.0 g ofa polymerization terminator was included, and 33 g of a solution, inwhich 30 wt % of WINGSTAY (Eliokem SAS, France), as an antioxidant, wasdissolved in hexane, were added. A polymer thus obtained was put in hotwater heated by steam and stirred to remove the solvent, and was thenroll-dried to remove the remaining solvent and water to prepare amodified butadiene polymer.

Example 4

900 g of 1,3-butadiene and 6.6 kg of n-hexane were added to a 20 Lautoclave reactor, and an internal temperature of the reactor was thenincreased to 70° C. After a catalyst composition, which was prepared bya reaction of a hexane solution, in which 0.10 mmol of Nd(2,2-diethyldecanoate)₃ was dissolved, with 0.89 mmol of diisobutylaluminum hydride(DIBAH), 0.24 mmol of diethylaluminum chloride, and 3.3 mmol of1,3-butadiene, was added to the reactor, polymerization was performedfor 60 minutes. Thereafter, a hexane solution including 0.23 mmol of themodifier represented by Formula 1-4, which was prepared in PreparationExample 4, was added, and a modification reaction was then performed at70° C. for 30 minutes. Thereafter, a hexane solution, in which 1.0 g ofa polymerization terminator was included, and 33 g of a solution, inwhich 30 wt % of WINGSTAY (Eliokem SAS, France), as an antioxidant, wasdissolved in hexane, were added. A polymer thus obtained was put in hotwater heated by steam and stirred to remove the solvent, and was thenroll-dried to remove the remaining solvent and water to prepare amodified butadiene polymer.

Comparative Example

900 g of 1,3-butadiene and 6.6 kg of n-hexane were added to a 20 Lautoclave reactor, and an internal temperature of the reactor was thenincreased to 70° C. After a catalyst composition, which was prepared bya reaction of a hexane solution, in which 0.10 mmol of Nd(2,2-diethyldecanoate)₃ was dissolved, with 0.89 mmol of diisobutylaluminum hydride(DIBAH), 0.24 mmol of diethylaluminum chloride, and 3.3 mmol of1,3-butadiene, was added to the reactor, polymerization was performedfor 60 minutes. Thereafter, a hexane solution, in which 1.0 g of apolymerization terminator was included, and 33 g of a solution, in which30 wt % of WINGSTAY (Eliokem SAS, France), as an antioxidant, wasdissolved in hexane, were added. A polymer thus obtained was put in hotwater heated by steam and stirred to remove the solvent, and was thenroll-dried to remove the remaining solvent and water to prepare abutadiene polymer.

Experimental Example 1

Physical properties of each of the modified butadiene polymers preparedin Examples 1 to 4 and the butadiene polymer prepared in ComparativeExample were respectively measured by the following methods, and theresults thereof are presented in Table 1 below.

1) Weight-Average Molecular Weight (Mw), Number-Average Molecular Weight(Mn), and Molecular Weight Distribution

Each polymer was dissolved in tetrahydrofuran (THF) at 40° C. for 30minutes, and then loaded and flowed into a gel permeation chromatography(GPC) column. In this case, as the column, two PLgel Olexis (productname) columns by Polymer Laboratories and one PLgel mixed-C (productname) column by Polymer Laboratories were combined and used. Also, allnewly replaced columns were mixed-bed type columns, and polystyrene wasused as a GPC standard material.

2) Mooney Viscosity and −S/R Value

Mooney viscosity (MV) of each polymer was measured with a large rotor ata rotor speed of 2±0.02 rpm at 100° C. using MV2000E by MonsantoCompany. After each polymer was left standing for 30 minutes or more atroom temperature (23±3° C.), 27±3 g of each polymer was taken as asample used in this case and filled into a die cavity, and Mooneyviscosity was measured while applying a torque by operating a platen.

Also, a change in the Mooney viscosity obtained while the torque wasreleased during the measurement of the Mooney viscosity was observed for1 minute, and a −S/R value was determined from its slope.

3) Cis-1,4 Bond Content

Fourier transform infrared spectroscopy was performed on each polymer,and a cis-1,4 bond content in the 1,4-cis polybutadiene was calculatedfrom the result thereof.

TABLE 1 Comparative Category Example 1 Example 2 Example 3 Example 4Example Whether or not Modified Modified Modified Modified Unmodifiedmodified GPC Mn (×10⁵ g/mol) 28.4 27.9 28.1 28.0 28.3 results Mw (×10⁵g/mol) 93.4 86.8 88.4 91.2 80.0 Mw/Mn 3.29 3.11 3.14 3.25 2.83 MV (ML1 +4, @100° C.) 50.1 50.6 48.4 49.7 45.0 (MU) −S/R 0.764 0.751 0.755 0.7470.694 Cis-1,4 bond 96.3 96.8 96.5 96.6 96.1 content (%)

As illustrated in Table 1, it was confirmed that the modified butadienepolymers of Examples 1 to 4 according to the embodiment of the presentinvention had a −S/R value of 0.7 or more which was significantlyincreased in comparison to the butadiene polymer of Comparative Example.From this result, it may be confirmed that the modified butadienepolymers according to the embodiment of the present invention had highlinearity.

Experimental Example 2

After rubber compositions and rubber samples were prepared by using themodified butadiene polymers prepared in Examples 1 to 4 and thebutadiene polymer prepared in Comparative Example, Mooney viscosity,300% modulus, and viscoelasticity were respectively measured by thefollowing methods. Among them, index values in the 300% modulus andviscoelasticity were expressed by indexing measurement values ofComparative Example at 100. The results thereof are presented in Table 2below.

Specifically, with respect to the rubber compositions, 70 parts byweight of carbon black, 22.5 parts by weight of process oil, 2 parts byweight of antioxidant (TMDQ), 3 parts by weight of zinc oxide (ZnO), and2 parts by weight of stearic acid were mixed with 100 parts by weight ofeach of the modified butadiene polymers and butadiene polymer to prepareeach rubber composition. Thereafter, 2 parts by weight of sulfur, 2parts by weight of a vulcanization accelerator (CZ), and 0.5 part byweight of a vulcanization accelerator (DPG) were added to each rubbercomposition, and vulcanization was performed at 160° C. for 25 minutesto prepare each rubber sample.

1) Mooney Viscosity (ML1+4)

Mooney viscosity of each rubber sample was measured with a large rotorat a rotor speed of 2±0.02 rpm at 100° C. using MV2000E by MonsantoCompany.

2) Tensile Strength (Kg·f/Cm²), 300% Modulus (Kg·f/Cm²), and Elongation

After the vulcanization of each rubber composition at 150° C. for 90minutes, tensile strength of each vulcanizate, a modulus at 300%elongation (M-300%), and an elongation of each vulcanizate at break weremeasured according to ASTM D412.

3) Viscoelasticity (Tan δ @60° C.)

With respect to Tan δ property that is most important for low fuelconsumption property, a viscoelastic coefficient (Tan δ) was measured ata frequency of 10 Hz, a prestrain of 5%, a dynamic strain of 3%, and atemperature of 60° C. using DMTS 500N by Gabo Instruments, Germany.

TABLE 2 Comparative Category Example 1 Example 2 Example 3 Example 4Example ML1 + 4   92.1   93.6   88.4   90.3  67 (FMB: Final Masterbatch) M-300% 110 112 106 108 101 (Index) (108) (110) (105) (107) (100)tan δ     0.134     0.132     0.137     0.135     0.142 @60° C. (106)(108) (104) (105) (100) (Index)

As illustrated in Table 2, it was confirmed that Mooney viscositycharacteristics, 300% moduli, and viscoelastic properties of the rubbersamples, which were prepared by using the modified butadiene polymers ofExamples 1 to 4 prepared by using the modifiers according to theembodiment of the present invention, were better than those of therubber sample prepared by using the butadiene polymer of ComparativeExample.

Specifically, with respect to the rubber samples which were prepared byusing the modified butadiene polymers of Examples 1 to 4 prepared byusing the modifiers according to the embodiment of the presentinvention, it was confirmed that tan δ values at 60° C. were reduced(indices were improved) while 300% moduli were significantly increasedin comparison to that of the rubber sample prepared by using theunmodified butadiene polymer of Comparative Example. The resultsindicated that the modified butadiene polymer prepared by using themodifier according to the embodiment of the present invention may havehigh fuel efficiency as well as excellent rolling resistance (RR)characteristics while having excellent tensile properties.

The invention claimed is:
 1. A modified conjugated diene-based polymercomprising a functional group derived from a modifier represented byFormula 1:

wherein, in Formula 1, R₁ is a monovalent hydrocarbon group having 1 to20 carbon atoms; or a monovalent hydrocarbon group having 1 to 20 carbonatoms which includes at least one heteroatom selected from the groupconsisting of nitrogen (N), sulfur (S), and oxygen (O), R₂ is a divalenthydrocarbon group having 1 to 20 carbon atoms which is substituted orunsubstituted with at least one substituent selected from the groupconsisting of an alkyl group having 1 to 20 carbon atoms, a cycloalkylgroup having 3 to 20 carbon atoms, and an aryl group having 6 to 30carbon atoms; or a divalent hydrocarbon group having 1 to 20 carbonatoms which includes at least one heteroatom selected from the groupconsisting of N, S, and O, and R₃ and R₄ are each independently amonovalent hydrocarbon group having 1 to 20 carbon atoms which issubstituted or unsubstituted with at least one substituent selected fromthe group consisting of an alkyl group having 1 to 20 carbon atoms, acycloalkyl group having 3 to 20 carbon atoms, and an aryl group having 6to 30 carbon atoms, or R₃ and R₄ are connected to each other to form analiphatic or aromatic ring having 5 to 20 carbon atoms.
 2. The modifiedconjugated diene-based polymer of claim 1, wherein the modifierrepresented by Formula 1 comprises compounds represented by Formulae 1-1to 1-4:


3. The modified conjugated diene-based polymer of claim 1, wherein thepolymer has a number-average molecular weight of 100,000 g/mol to700,000 g/mol.
 4. The modified conjugated diene-based polymer of claim1, wherein the polymer has a molecular weight distribution (Mw/Mn) of1.05 to
 5. 5. The modified conjugated diene-based polymer of claim 1,wherein the polymer has a −S/R (stress/relaxation) value at 100° C. of0.7 or more.
 6. A method of preparing the modified conjugateddiene-based polymer of claim 1, the method comprising: (1) preparing anactive polymer coupled with an organometal by polymerization of aconjugated diene-based monomer in a hydrocarbon solvent in the presenceof a catalyst composition including a lanthanide rare earthelement-containing compound; and (2) reacting the active polymer with amodifier represented by Formula 1:

wherein, in Formula 1, R₁ is a monovalent hydrocarbon group having 1 to20 carbon atoms; or a monovalent hydrocarbon group having 1 to 20 carbonatoms which includes at least one heteroatom selected from the groupconsisting of nitrogen (N), sulfur (S), and oxygen (O), R₂ is a divalenthydrocarbon group having 1 to 20 carbon atoms which is substituted orunsubstituted with at least one substituent selected from the groupconsisting of an alkyl group having 1 to 20 carbon atoms, a cycloalkylgroup having 3 to 20 carbon atoms, and an aryl group having 6 to 30carbon atoms; or a divalent hydrocarbon group having 1 to 20 carbonatoms which includes at least one heteroatom selected from the groupconsisting of N, S, and O, and R₃ and R₄ are each independently amonovalent hydrocarbon group having 1 to 20 carbon atoms which issubstituted or unsubstituted with at least one substituent selected fromthe group consisting of an alkyl group having 1 to 20 carbon atoms, acycloalkyl group having 3 to 20 carbon atoms, and an aryl group having 6to 30 carbon atoms, or R₃ and R₄ are connected to each other to form analiphatic or aromatic ring having 5 to 20 carbon atoms.
 7. The method ofclaim 6, wherein the catalyst composition is used in an amount such thatthe lanthanide rare earth element-containing compound is included in anamount of 0.1 mmol to 0.5 mmol based on 100 g of the conjugateddiene-based monomer.
 8. The method of claim 6, wherein the lanthaniderare earth element-containing compound comprises a neodymium-basedcompound represented by Formula 5:

wherein, in Formula 5, R_(a) to R_(c) are each independently hydrogen oran alkyl group having 1 to 12 carbon atoms, but all of R_(a) to R_(c)are not hydrogen at the same time.
 9. The method of claim 6, wherein themodifier is used in an amount of 0.5 mol to 20 mol based on 1 mol of thelanthanide rare earth element-containing compound.